Effects of the essential oil cyclodextrin complexes on ruminal methane production in vitro

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ABSTRACTThe effects of including essential oil cyclodextrin (CD) complexes on ruminal methane and hydrogen production, volatile fatty acid (VFA) and protozoa were studied in vitro. The essential oil CD complexes used in the present study were both αCD and βCD with cineol, eucalyptus, menthol, peppermint, thyme and wasabi. Diluted rumen fluid (60 mL) was incubated anaerobically at 38°C for 6 h with the essential oil CD complex (1–40 mg as oil). Eucalyptus‐αCD reduced methane production by 40% with 10 mg as oil along with decreasing the protozoal number and increasing total VFA and proportion of propionic acid. Both wasabi‐αCD and wasabi‐βCD reduced methane production by 85% and 97%, respectively, with 10 mg as oil, though they increased hydrogen production notably. The protozoal number was unchanged by wasabi‐βCD and decreased to 50% by wasabi‐αCD. Propionic acid was increased by both wasabi‐αCD and wasabi‐βCD. The other essential oil‐CD showed no significant effect on reducing methane production. The combined use of 20 mM of fumaric acid with wasabi‐αCD (1 mg as oil) caused about a 50% depression of methane production compared to the control without increasing hydrogen production. Fumaric acid was more effective than malic acid in reducing methane production. The addition of eucalyptus‐αCD, wasabi‐αCD or wasabi‐βCD together with organic acid to rumen fluid turned out to be effective for reducing methane production with no increase in hydrogen production.